LISP to Ruby translation

Ruby
1

Jut a quick one, how do you translate this:

((if (zero? 0) + -) 3 4)
=> 7

to Ruby?

Cheers,
Douglas

2

Douglas L. wrote:

Jut a quick one, how do you translate this:

((if (zero? 0) + -) 3 4)
=> 7

to Ruby?

Cheers,
Douglas

3.send(x.zero? ? :+ : :-, 4)

It’s a little hard to read with all those colons. Maybe this is better:

3.send(if x.zero? then :+ else :- end, 4)

Or you could replace symbols with strings for readability, at a cost to
speed:

p 3.send(x.zero? ? “+” : “-”, 4)

3

Douglas L. wrote:

Jut a quick one, how do you translate this:

((if (zero? 0) + -) 3 4)
=> 7

to Ruby?

Well, these kind of questions are rarely helpful; translating an
idiomatic expression out of context from one language is often useless,
because in a greater context the ruby code might be doing something
completely different to begin with.

But, if you want a one-liner…

3.method(0.zero? ? :+ : :-).call(4)

–
Neil S. - [email protected]

‘A republic, if you can keep it.’ – Benjamin Franklin

4

Douglas L. wrote:

Just a quick one, how do you translate this:

((if (zero? 0) + -) 3 4)

What dialect of LISP is that? Not Common… CL has no “zero?”
(it’s “zerop”), and + and - refer to input history rather than the
functions
associated with the operators. To do something like that in CL I think
you have to use the characters '+ and '- and an (eval)…

5

On Fri, Dec 16, 2005 at 07:22:39AM +0900, Mark J.Reed wrote:

Douglas L. wrote:

Just a quick one, how do you translate this:

((if (zero? 0) + -) 3 4)

What dialect of LISP is that? Not Common… CL has no “zero?”

It’s Scheme. A much nicer dialect than CL, IMHO. :wink:

I think in CL the equivalent would be:

((if (zerop 0) #’+ #’-) 3 4)

Note the ugly sharp-quotes, due to the fact that CL has separate
namespaces for values and functions.

regards,
Ed

6

Stephen W. wrote:

–Steve

7

7

On Dec 14, 2005, at 6:36 PM, Douglas L. wrote:

((if (zero? 0) + -) 3 4)
=> 7

to Ruby?

7 if true

–Steve

8

Edward F. [email protected] writes:

I think in CL the equivalent would be:

((if (zerop 0) #‘+ #’-) 3 4)

No, you need:

(apply (if (zerop 0) #‘+ #’-) '(3 4))

Note the ugly sharp-quotes, due to the fact that CL has separate
namespaces for values and functions.

And that is why. :slight_smile:

9

Joel VanderWerf [email protected] wrote:

7 if true

–Steve

7

There - who says ruby isn’t concise!

martin